1. Technical Field
The invention relates generally to an assembly system and more specifically to a scheduling optimizer for a device, such as a semiconductor, assembly system.
2. Related Art
Devices, such as semiconductor components, Cathode-ray tubes, hard drives, and other electronic and non-electronic devices in a manufacturing environment may be sensitive to several different types of activities or events as they are being manufactured. These activities and other factors may produce a failure of the device, especially in the case that the device is an electronic component that may be impaired or destroyed from electrical overstress (EOS), electrostatic discharge (ESD) or latch-up.
EOS, ESD and latch-up are concerns in both internal and peripheral circuitry of a device. Specifically, ESD activities may influence, to name a few, off-chip drivers, ESD networks, transmitter and receiver networks, system clocks, phase lock loops, capacitors, decoupling capacitors and fill shapes. ESD activities may also influence DRAM memory, SRAM memory, gate arrays, and logic circuitry. Latch-up may occur between interactions within a given circuit, or between circuits. Latch-up may also be an inter-circuit or intra-circuit interaction.
Several activities or factors that may cause ESD, EOS or latch-up in electronic components include: the environment through which the device is routed; the shipping of the device; shipping container types; machines used to assemble the device; extent of handling of the device; device design; fabrication technology; device package style; and/or tools used in the manufacturing of the device. Specifically, with environmental conditions, humidity influences the ESD discharge process and the level of potential risk to the device. Dry environments can lead to a higher ESD discharge event, leading to a higher risk to device failure. High humidity leads to a lower ESD discharge event. With shipping of the device, ESD failures may be influenced, for example, by the motion, material properties of the shipping containers and vehicles, and/or the percentage of material, including the devices, within each shipping container. Electromagnetic emissions (EMI) noise can also induce ESD activities during shipping and handling.
Failures may occur at different stages of the manufacturing and assembly of the device prior to the final device development. ESD failures may occur on wafers, diced devices, and packaged and unpackaged components. With automated material handling systems (AMHS), the movement of assembly lots of devices between stocking points, bays, and individual tools may be done without human operators through a floor schedule. But even without human operators, the device may be sensitive to different types of machines or mechanisms with various levels of sensitivity at different points of the assembly of the device.
Currently, there are a variety of industry standard methods that are used for reducing ESD failure rates (e.g., humidity control) in the assembly of a device. Some of these methods may be selectively applied with the assembly of the device. Although these methods may reduce specific ESD sensitivities, other ESD sensitivities may occur with the assembly of the device that may not be noticed until the device or other devices fail. Consequently, modifications to the floor schedule of an assembly unit (e.g., the tools, systems, methods, etc., that are used or available for use in a manufacturing environment to assemble a device, or a group of devices, such as an assembly lot) that could reduce other occurring ESD sensitivities may not be made until many devices have failed, thus, negatively affecting the yield loss of the assembly.
Accordingly, a need has developed in the art for a system and method that analyzes a device for sensitivities, such as ESD sensitivities, and allows for modification of a floor schedule of an assembly unit based on the sensitivity of the device while improving the overall performance of the assembly unit.